Field of the Invention
The present invention relates to an apparatus, system, and method of inspecting an image formed by an image forming apparatus, and a recording medium storing an image inspection control program.
Description of the Related Art
Conventionally, the inspection of printed matter has been performed by human operators. In recent years, inspection apparatuses that automatically inspect printed matter have been widely used, mainly in the field of offset printing. For example, in conventional devices, a master image is generated by reading specific printed matter that is selected based on the image quality, as a reference image. The corresponding portions of the master image and a subsequently read image of printed matter would be compared to determine, by the degree of difference therebetween, whether there was a defect in the printed matter.
Printing apparatuses, such as electrophotographic apparatus, have been widely used to print a small number of pages. For example, a printing apparatus may perform variable printing in which the printed contents differ on each page. In such case, comparing the printed matter with the master image generated from the previously printed matter would be inefficient. In view of this, the master image has typically been generated based on print data and then compared with the printed image to be inspected.
With respect to the comparing inspection of the image, Japanese Patent Application Publication No. 2006-007659-A proposes a method of generating image data of a defective part in a resolution higher than at the time of the inspection of the printed matter in which the defect was detected, and enlargedly displaying an enlarged depiction of the defective part.
In consideration of a position shift with the master image and the read image of the printed matter, a comparison process can be performed multiple times while shifting the master image and the read image vertically and horizontally. Utilization of the comparison result of a state with few degrees of the difference can also be performed. Accordingly, since the starting point at the time of comparing the master image with the read image is set as correctly as possible, position alignment with the master image and the read image may be performed utilizing the comparison process and shifting of the images vertically and horizontally.
Moreover, the position alignment of the master image and the read image of printed matter involves performing a rotational correction process with respect to one side based on a certain reference point. As a reference point, a printer's mark used as the mark of a cutting and some characterizing portions (i.e., a corner part, etc.) in an image can be used.
However, a reference point suitable for position alignment cannot always be extracted from an image. Therefore, when a reference point suitable for position alignment cannot be extracted, the rotational correction process may become inadequate for aligning the read image and the master image. If a shift has arisen such that position alignment is inadequate in the comparison area of both images, it may be determined that there is a defect despite normal printed matter if during inspection it is determined that the degree of the difference is high.
Accordingly, in order to provide a more accurate inspection, the range over which the image is shifted vertically and horizontally in the case of the comparison of the read image and the master image is extended. Each difference value is then calculated and considered in order to extract a reference point suitable for position alignment. However, such a process may increase the computation time and when the processing time for an inspection has restrictions, such as the processing capacity of an inspection apparatus, the inspection process may end in the middle of a calculation due to the restrictions on processing time. In such an instance, the inspection process may not be completed and the correct result may not be obtained and it may be erroneously determined that the printed matter has a defect.
Accordingly, during the inspection of the printed matter by an inspection apparatus, even though there is no defect in the printed matter it may be determined that a defect exists in the printed matter based on a defect in the position alignment thereby providing an incorrect inspection result. Therefore, the user will then need to confirm whether the printed matter judged to be defective is truly defective thereby creating a large burden for the user. Moreover, even if it is a case where the technique of JP No. 2006-007659-A is employed such that the resolution of the defective part of the printed matter is made high and is prominently displayed, it still cannot be determined whether the printed matter truly contains a defect without confirmation from a user.